1. Field of the Invention
The present invention relates to a wireless communication system including a base unit and two or more remote units (handsets), in which system direct communication can be performed between two handsets.
2. Description of the Related Art
In bi-directional communications performed by conventional cordless telephones, a base unit transmits data to a remote unit at a frequency f1; and the remote unit transmits data to the base unit using another frequency f2. However, when using a system with this arrangement and having two or more remote units with one base unit, it has not been possible to perform communications directly between two remote units (hereinafter referred to as remote-to-remote communication). Direct communication has only been possible between the base unit and a remote unit (hereinafter also referred to as base-to-remote communication). That is, data transmitted by a first remote unit at a frequency f2 can only be received by the base unit, which is designed to receive frequency f2, and cannot be received by a second remote unit, which is designed to receive a frequency f1.
Cordless telephones that perform frequency hopping spread spectrum communications between a base unit and remote units are well known in the art. During communication operations, this type of cordless telephone employs a prearranged frequency switching order called a hopping pattern. Both the base unit and remote units communicate using the same hopping pattern.